Loci conferring disease and pest resistance have been identified in many plant species. Genetic analysis of many plant-pathogen interactions has demonstrated that plants contain loci that confer resistance against specific races of a pathogen containing a complementary avirulence gene. Molecular characterization of these genes should provide means for conferring disease resistance to a wide variety of crop plants.
Plant parasitic nematodes are significant pest in many parts of the world. Especially significant in terms of crop losses are the sedentary endo-parasites, cyst nematodes (Globodera spp. and Heterodera spp.) and root-knot nematodes (Meloidogyne spp.).
A number of plant resistance genes that have been characterized at the molecular level (see, e.g., Staskawicz et al., Science 268:661-667 (1995)). The derived amino acid sequences of the most common class all contain leucine-rich repeats (LRR) and nucleotide binding sites (NBS). Examples included RPS2, RPM1 (bacterial resistances in Arabidopsis; Mindrinos et al. Cell 78:1089-1099 (1994)); Bent et al. Science 265:1856-1860 (1994); Grant et al., Science 269:843-846 (1995)), L6 (fungal resistance in flax; Lawrence, et al., The Plant Cell 7:1195-1206 (1995)), and N, (virus resistance in tobacco; Whitham, et al., Cell 78:1101-1115 (1994); and U.S. Pat. No. 5,571,706).
The NBS is a common motif in several mammalian gene families encoding signal transduction components (e.g., Ras) and is associated with ATP/GTP-binding sites. LRR domains can mediate protein-protein interactions and are found in a variety of proteins involved in signal transduction, cell adhesion and various other functions. LRRs are leucine rich regions often comprising 20-30 amino acid repeats where leucine and other aliphatic residues occur periodically. LRRs can function extracellularly or intracellularly.
Today, nematode and other pests are controlled primarily using chemical pesticides. These compounds are generally very toxic and have been suspected of causing environmental damage. These concerns have prompted efforts to find other methods of controlling nematodes in economically important crop plants. The present invention addresses these and other needs.